1. Field of the Invention
The present invention relates to a stepping motor driver which drives a stepping motor for control of the position and speed of driven equipment.
2. Description of the Prior Art
In most conventional stepping motors, a current command is fixed.
Therefore, there is a problem that a stepping motor consumes much power and is less efficient because a fixed current flows even while it is stopped or running at a low speed.
As a solution to this problem, the following approach to reduce power consumption has been taken: during motor running, a command for a current which is enough to generate a required torque is selected and upon elapse of a given time after a motor stop, the value of the current command is decreased to the necessary minimum.
However, even in this case, since the exciting current of the stepping motor is controlled with a fixed current command during motor running, its power consumption is considerable and its efficiency is low. Also, in the event that a high speed-response is required, it is impossible to power up the torque output of the stepping motor.